Engine starter gearing



May 4, 1943. o. P. KEARNEY ENGINE STARTER GEARING Filed March 3, 1942 INVENTOR. BY UMP/Carney Patented May 4, 1943 ENGINE STARTER GEARING Daniel P. Kearney, Birmingham, Mich., assignor to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application March 3, 1942, Serial No. 433,109

4 Claims.

The present invention relate to engine starter gearing and more particularly to a detent arrangement for ensuring traversal of a starter drive pinion.

In starter drives of the type in which a pinion is provided with a threaded connection to the starting motor for traversing the pinion into mesh with an engine gear, various forms of detent have been proposed for opposing initial rtation of the pinion in order to ensure its traversal.

It is an object of the present invention to provide a novel arrangement of this kind which is simple in construction and automatic in its op eration to ensure mesh of the pinion without causing the pinion to attempt to re-mesh after the engine has started.

It is another object to provide such a device which may readily be arranged to occupy a small amount of space, without necessitating any projections from the exterior of the motor housing such as might interfere with its installation.

It is'another object to provide such a device in which the detent is withdrawn promptly after accomplishing its function, and is held retracted for a predetermined time after deenergization of the starting motor.

It is another object to provide such a device which incorporates a thermostat arranged to normally hold the detent in operative position with means for heating the thermostat electrically during the cranking operation in order to retract the detent.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation partly broken away and in section of a starter drive embodying a preferred form of the invention, and

Fig. 2 is a section taken substantially on the line 2-2 of Fig. 1.

In the drawing there is illustrated a drive shaft l joumalled in a housing 2 and rotated by reduction gearing 3 and 4 from a shaft 5 which may be the extended armature shaft of a starting motor not illustrated.

The drive shaft l is threaded for a portion of its length as indicated at B, and an internally threaded pinion l is mounted thereon for longitudinal movement into and out of engagement with a member such as a ring gear 8 of an engine to be started.

The pinion is normally maintained in its idle position as illustrated by means of a thrust collar 9 slidably mounted on a reduced smooth portion l l of the shaft and yieldingly held against the adjacent end of the threaded portion 6 by means of an anti-drift spring l2. Means for energizing the starting motor to project the pinion into engagement with the engine gear and thereafter to crank the engine is illustrated in the form of a battery 13 grounded at M and connected through a starting switch I5 to the starting motor which is grounded in the usual way to complete the starting circuit. The operative position of the pinion is defined by an abutment and bearing member ID for the collar 9 fixed on the end of shaft I.

According to the present invention means are provided for opposing initial rotation of the pinion when in idle position in order to ensure its traversal into mesh with the engine gear upon actuation of the starting motor. As here shown this means is in the form of a detent member I6 mounted on the free end of a metallic blade member I! which is anchored to the housing as shown at l8 in position to cause the detent IE to engage between the teeth of the pinion I when it is in normal position as shown. The detent is so positioned that when the pinion moves into operative position it is disengaged from the detent and is thereby free to rotate without interference.

Means for retracting the detent from operative position to prevent its interfering with the de-meshing of the pinion, or causing the pinion to attempt to re-mesh, is provided by forming the blade l'l out of bimetallic material arranged when heated to bend upward and raise the detent from the path of the pinion l, and by providing heating means 22 for such thermostatic element which is effective during the cranking operation. For this purpose, the blade I! is insulated from the housing 2 as indicated at [9, and from the detent [6 as shown at l9, and is connected to the starting motor lead at the starting switch l5 by means of a lead 2|. A contact 23 is fixed on the blade l1, and a grounding contact therefor is pivotally mounted on the driving shaft I as by means of a pin 25 (Fig. 2) in position to be moved by centrifugal force into wiping engagement with the contact 23. Centrifugal contact 20 is normally held retracted by a spring 24, and its outward movement is limited by suitable means such as a pin 26.

In operation, starting with the parts in the positions illustrated, closure of the starting switch l5 energizes the starting motor, which causes rotation of the drive shaft I in the direction of the arrow a. Since the inion 1 is held from rotation by the detent IE, it is caused to traverse into mesh with the engine gear 8 and when fully meshed is constrained to rotate with the drive shaft and crank the engine. At this time the pinion has moved beyond the detent l6 which accordingly does not interfere with the rotation of the pinion.

Rotation of the drive shaft causes the contact 20 to swing outward under centrifugal force and engage and ground the contact 23, whereby a current is caused to flow through the thermostatic blade ll, causing it to bend upward and retract the detent, at the same time drawing the contact 23 out of the path of the centrifugal contact 20.

If the engine immediately becomes self-operative, the pinion is returned to its idle position by the acceleration of the engine gear, whereupon the operator opens the starting switch and the thermostat cools off and returns the detent IE to normal position. If the cranking operation continues for a considerable period of time, the thermostat I! may cool off somewhat from time to time, permitting the contact 22 to momentarily re-engage the contact 23, thus re-heating the thermostat and keeping the detent l6 retracted from the path of the pinion. It will thus be seen that the detent is maintained retracted during the cranking operation and for a predetermined time thereafter, sufl'icient to allow the starting motor to come to rest.

,Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starter drive a drive shaft, a pinion having a threaded connection therewith, a detent normally engaging the pinion to resist rotation thereof, thermostatic means normally holding the detent in engagement with the pinion and means for heating the thermostatic means to withdraw the detent, and means responsive to rotation of the drive shaft above a predetermined speed for causing energization of the heating means.

2. In an engine starter drive a drive shaft, a pinion having a threaded connection therewith, a detent normally engaging the pinion to resist rotation thereof, thermostatic means normally holding the detent inengagement with the pinion, and electrical heating means for the thermostat including a centrifugal switch closed by rotation of the drive shaft above a predetermined speed.

3. In. an engine starter drive a power shaft, a pinion having a threaded connection therewith,

a thermostatic arm anchored at one end and hav ing a detent on its free end adapted to engage and oppose rotation of the pinion, and electrical heating circuit for the thermostat including a pair of normally open contacts, and centrifugal means on the drive shaft for closing said tacts. 1

4. In an engine starter drive a power shaft,

a pinion having a threaded connection therewith,- a thermostatic arm anchored at one end and hav-' ing a detent on its free end adapted to engage and oppose rotation of the pinion, an electrical 

